The operator control circuit for a fork lift truck or the like normally includes a plurality of handles pivotally mounted on a console for selectively effecting the lift, tilt and auxiliary functions of the lift truck. Each handle normally simultaneously actuates a hydraulic control valve and a potentiometer which controls the speed of an electrical motor which, in turn, controls the speed of a pump. The pump is adapted to communicate pressurized fluid to a hydraulic cylinder of the control circuit, through the control valve, for performing a particular work task. A conventional control circuit of this general type is fully disclosed in U.S. Pat. No. 3,962,871, assigned to the assignee of this application.
It has proven desirable to provide adjustment means whereby relative movement between a housing and rotary adjustment shaft of the potentiometer may be varied in response to pivotal movement of a control handle connected thereto. Such adjustment not only facilitates utilization of substantially identical control arrangements for effecting varying ranges of motor speeds, but also permits the operator to readjust a particular motor speed range for a particular work function, if so desired. For example, the operator may want to be afforded the option of a high or relatively low motor speed while utilizing an auxiliary work implement or attachment mounted on the lift truck.